The navies of Japan, the Philippines, and the United States carried out a multilateral Maritime Cooperative Activity (MCA) in the South China Sea on September 13, 2025, underscoring their shared commitment to a Free and Open Indo-Pacific (FOIP) and the defense of international maritime law.
According to a news release from the Embassy of Japan in Manila, the exercise featured the Japan Maritime Self-Defense Force (JMSDF) vessel JS Osumi (LST-4001), alongside Philippine Navy and US Navy ships and aircraft.
The drills typically include search and rescue operations, coordinated naval maneuvers, and surveillance exercises—activities designed to sharpen interoperability and strengthen crisis readiness among the three allies.
Officials said the MCA reflects the partners’ resolve to uphold the United Nations Convention on the Law of the Sea (UNCLOS) and reinforce a rules-based order in the region.
The three countries reaffirmed their unwavering partnership in the region and will continue to work in close coordination to uphold lasting peace, prosperity, and security, the Japanese Embassy in Manila said.
The MCA, now in its 11th iteration, is part of a series of joint naval drills increasingly held in both the South China Sea and West Philippine Sea. These activities demonstrate operational readiness and coordinated response capabilities, ranging from anti-submarine warfare and interdiction to amphibious operations and cross-deck landings.
Assets that have participated include the Philippine Navy’s BRP Jose Rizal, the US Navy’s USS John Finn and P-8A Poseidon aircraft, and the JMSDF’s JS Osumi and JS Noshiro.
Earlier this year, the three countries also held trilateral coast guard drills, including in Japanese waters, linked to the newly expanded Reciprocal Access Agreements (RAA) that allow smoother joint operations.
The Zambales-based exercises from September 12–13, off Magalawa and Silanguin Islands, came as China announced the establishment of a so-called marine reserve at Scarborough Shoal (locally called Panatag Shoal), a traditional fishing ground well within the Philippines’ Exclusive Economic Zone (EEZ). The move has fueled concerns of further escalation in contested waters.
By staging these joint maritime activities, Manila, Tokyo, and Washington signal their intent to counter unilateral actions and maintain stability in one of the world’s most contested maritime zones.